package ssen.common {
import flash.utils.ByteArray;

public class Base64 {
	private static const BASE64_CHARS:String = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/=";
	
	public static const version:String = "1.1.0";
	
	public static function encode(data:String):String {
		// Convert string to ByteArray
		var bytes:ByteArray = new ByteArray();
		bytes.writeUTFBytes(data);
		
		// Return encoded ByteArray
		return encodeByteArray(bytes);
	}
	
	public static function encodeByteArray(data:ByteArray):String {
		// Initialise output
		var output:String = "";
		
		// Create data and output buffers
		var dataBuffer:Array;
		var outputBuffer:Array = new Array(4);
		
		// Rewind ByteArray
		data.position = 0;
		
		// while there are still bytes to be processed
		while (data.bytesAvailable > 0) {
			// Create new data buffer and populate next 3 bytes from data
			dataBuffer = new Array();
			
			for (var i:uint = 0; i < 3 && data.bytesAvailable > 0; i++) {
				dataBuffer[i] = data.readUnsignedByte();
			}
			
			// Convert to data buffer Base64 character positions and 
			// store in output buffer
			outputBuffer[0] = (dataBuffer[0] & 0xfc) >> 2;
			outputBuffer[1] = ((dataBuffer[0] & 0x03) << 4) | ((dataBuffer[1]) >> 4);
			outputBuffer[2] = ((dataBuffer[1] & 0x0f) << 2) | ((dataBuffer[2]) >> 6);
			outputBuffer[3] = dataBuffer[2] & 0x3f;
			
			// If data buffer was short (i.e not 3 characters) then set
			// end character indexes in data buffer to index of '=' symbol.
			// This is necessary because Base64 data is always a multiple of
			// 4 bytes and is basses with '=' symbols.
			for (var j:uint = dataBuffer.length; j < 3; j++) {
				outputBuffer[j + 1] = 64;
			}
			
			// Loop through output buffer and add Base64 characters to 
			// encoded data string for each character.
			for (var k:uint = 0; k < outputBuffer.length; k++) {
				output += BASE64_CHARS.charAt(outputBuffer[k]);
			}
		}
		
		// Return encoded data
		return output;
	}
	
	public static function decode(data:String):String {
		// Decode data to ByteArray
		var bytes:ByteArray = decodeToByteArray(data);
		
		// Convert to string and return
		return bytes.readUTFBytes(bytes.length);
	}
	
	public static function decodeToByteArray(data:String):ByteArray {
		// Initialise output ByteArray for decoded data
		var output:ByteArray = new ByteArray();
		
		// Create data and output buffers
		var dataBuffer:Array = new Array(4);
		var outputBuffer:Array = new Array(3);
		
		// While there are data bytes left to be processed
		for (var i:uint = 0; i < data.length; i += 4) {
			// Populate data buffer with position of Base64 characters for
			// next 4 bytes from encoded data
			for (var j:uint = 0; j < 4 && i + j < data.length; j++) {
				dataBuffer[j] = BASE64_CHARS.indexOf(data.charAt(i + j));
			}
			
			// Decode data buffer back into bytes
			outputBuffer[0] = (dataBuffer[0] << 2) + ((dataBuffer[1] & 0x30) >> 4);
			outputBuffer[1] = ((dataBuffer[1] & 0x0f) << 4) + ((dataBuffer[2] & 0x3c) >> 2);
			outputBuffer[2] = ((dataBuffer[2] & 0x03) << 6) + dataBuffer[3];
			
			// Add all non-padded bytes in output buffer to decoded data
			for (var k:uint = 0; k < outputBuffer.length; k++) {
				if (dataBuffer[k + 1] == 64)
					break;
				output.writeByte(outputBuffer[k]);
			}
		}
		
		// Rewind decoded data ByteArray
		output.position = 0;
		
		// Return decoded data
		return output;
	}
	
	public function Base64() {
		throw new Error("Base64 class is static container only");
	}
}
}
